1. Field of the Invention
This invention relates generally to the cleaning of contaminates from substrate surfaces and, in particular, to the fabrication of electronic components such as integrated circuit semiconductors wherein particulate contaminates are removed from the surface of substrates such as semiconductor wafers used to make the electronic component.
2. Description of Related Art
The fabrication of electronic components such as integrated circuit semiconductors is very exacting and complex and requires a number of processing steps requiring extreme precision to form the desired circuit pattern on the component substrate. Typical semiconductor devices now have circuit line widths typically less than 0.5 micron with close spacing of the lines and via interconnections. Contamination of the semiconductor substrate in the form of particles on the substrate surface may cause short circuits, open circuits and other defects which can cause the component to fail and/or adversely affect the performance of the component. For example, an individual particle as small as 100 angstroms in diameter can result in a defect in a modern microcircuit electronic component.
Cleaning the surface of the semiconductor substrate is therefore a critical step in integrated circuit fabrication and periodic cleaning of the substrate during the fabrication process is needed to maintain product integrity. There are currently numerous methods used to clean substrate surfaces in the electronic industry and basically water or solvents or chemical cleaning are used to remove contaminate particles and films from the surfaces. Chemical solutions are typically combined with megasonic or ultrasonic devices wherein the component to be cleaned is immersed in the chemical solution and the megasonic or ultrasonic devices used to impart high energy sonic waves to the surface of the component which in combination with the chemical solution removes organic films, ionic impurities and contaminate particles from the substrate surface.
A number of cleaning methods are described in U.S. Pat. No. 5,062,898. For example, gas jet cleaning and liquid spray cleaning are used to clean relatively large particles from silicon wafers. Another cleaning technique involves the use of a carbon dioxide aerosol to xe2x80x9csand blastxe2x80x9d a contaminated surface.
A process for removing undesired sub-micron particles from a substrate is shown in U.S. Pat. No. 5,456,759 wherein the substrate to be cleaned is placed in a cleaning chamber provided with megasonic energy-producing means. A liquified gas such as liquid carbon dioxide is introduced into the cleaning chamber and the substrate subjected to the liquid carbon dioxide agitated using megasonic energy.
U.S. Pat. Nos. 5,690,749; 5,753,563 and 5,902,678 disclose the use of adhesive tapes which are applied to the surface of a semiconductor and then pulled therefrom to remove particles from the surface of the semiconductor which adhere to the adhesive tape. Japanese Patent No. 6260464 irradiates a cleaned-up mask with laser beams to detect any bonded foreign matter and then an adhesive head discharging a specific amount of adhesive is shifted on the position detected by the sensor to pressure-weld the adhesive head around the foreign matter to remove the foreign matter.
Wafer contamination is still a problem in the electronics and semiconductor fabrication industry however, and as the industry advances and technology is being developed to form smaller and more complex circuits, a more effective and efficient cleaning method to remove particulate foreign matter from substrates is required to produce electronic and semiconductor components.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method for removing contaminating particulate matter from a surface such as a wafer substrate used to make electronic components such as semiconductors.
It is a further object of the present invention to provide an apparatus for removing contaminating particulate matter from a surface such as wafer substrates used to make electronic components such as semiconductor wafers.
It is another object of the present invention to provide electronic component substrates including semiconductor wafers which have been cleaned using the method and apparatus of the invention.
Another object of the invention is to provide electronic components made using electronic component substrates cleaned using the method and apparatus of the invention.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method for removing contaminate particulate matter from a contaminate particle containing substrate surface such as a semiconductor wafer comprising the steps of:
applying a sacrificial coating of a material, preferably a fluid material, to a substrate surface containing undesirable particulate matter thereon, which material is to encapsulate and suspend the undesirable particles therein;
fluidizing the material if necessary;
applying energy to the coated substrate to dislodge at least some of the particulate matter from the surface of the substrate into the sacrificial coating such that the particulate matter is partially or fully encapsulated and suspended within the sacrificial coating forming a particulate matter containing sacrificial material coating; and
removing the particulate matter containing sacrificial material coating from the substrate surface providing a substrate surface having less particulate matter thereon.
In another aspect of the invention the coating material is a film forming liquid polymer such as polyimide or other such material which, after dislodging the particulate matter, is formed into a flexible film having a strength sufficient for the film to be removed by e.g., pulling the film from the substrate surface.
In an additional aspect of the invention, the energy supplied to the coated substrate to dislodge particulate matter into the sacrificial coating may be sonic, vibrational, centrifugal, and the like, depending on the substrate and/or apparatus used to coat and support the substrate to be cleaned. The energy may be applied to the coated substrate before, during and after application of the sacrificial material coating. The energy may also be applied during forming of the sacrificial material coating into a removable film.
In one aspect, it is contemplated that the substrate will be inclined so that a sacrificial material applied to the upper part of the substrate surface will flow downward over the surface removing particulate matter therefrom.
In a further aspect of the invention the energy applied to dislodge at least some of the contaminating particles from the surface of the substrate into the sacrificial material coating on the surface of the wafer is sonic energy such as ultrasonic energy or megasonic energy.
In still another aspect of the present invention, an apparatus is provided for removing contaminate particulate matter from a contaminate particle containing substrate surface such as a semiconductor wafer comprising:
a support for supporting a substrate containing undesirable particulate matter on the surface of the substrate;
means for applying a sacrificial material coating, preferably a fluid material, on the surface of the substrate, which material is to encapsulate and suspend the undesirable particles therein;
means for fluidizing the material if necessary;
energy forming means to dislodge at least some of the particulate matter from the surface of the substrate into the sacrificial material coating such that the particulate matter is partially or fully encapsulated and suspended within the sacrificial material coating forming a particulate matter containing sacrificial material coating; and
means for removing the particulate matter containing sacrificial material coating from the surface of the substrate providing a cleaned substrate surface.
In an additional aspect of the invention the sacrificial coating material is a film forming liquid polymer such as polyimide or other such material which, after dislodging the particulate matter, is formed into a flexible film having a strength sufficient for the film to be removed by, e.g., pulling the film from the substrate surface.
In a further aspect of the invention, the sacrificial material removal means is supplied by inclining the substrate so that a sacrificial material applied to the upper part of the substrate surface will flow downward over the substrate removing particulate matter therefrom.
In another aspect of the present invention, the method and apparatus of the invention may be employed to clean a variety of surfaces having contaminate particles thereon such as circuit boards, medical instruments and optical lenses as well as semiconductor wafers and other substrates used in electronic component fabrication.